Antibiotic resistant bacteria (ARB) and genes (ARGs) in urban wastewater treatment plants: influencing factors, mechanisms, and removal efficiency

Abstract

Urban wastewater treatment plants (UWWTPs) are major sources of antibiotic-resistant bacteria (ARB) and genes (ARGs) in the environment. Mitigating their impact requires understanding their sources, proliferation factors, and treatment mechanisms. While several studies have examined ARB and ARG concentrations and persistence post-effluent discharge, there is limited research on how intrinsic, environmental, and operational factors influence their prevalence. Notably, comprehensive decision-making tools for technology selection are lacking. We critically reviewed the sources of ARGs and ARB, factors influencing their fate, and the effectiveness of treatment processes. Our review highlights recent advances in monitoring and optimization and presents a decision matrix to guide selection of treatment technologies. Domestic wastewater had the highest relative ARG abundance while hospital wastewater, though lower in relative abundance, harbors greater ARG diversity. Due to their adaptability, ARGs persist even after organic and nutrient (energy source) removal, as bacterial lysis releases intracellular ARGs, which convert to extracellular ARGs. The fate of ARB and ARG depends on the form of organic matter – soluble or suspended - in the wastewater with soluble organic matter aiding removal via adsorption and complexation. Conventional primary and secondary treatment processes are less effective than advanced methods like chlorine disinfection and UV radiation, though efficiency varies with ARG type, reaction time, dosage. Combining different advanced treatments can improve ARG removal. Future research should explore pretreating different wastewater before discharge to UWWTP, bacteriophage roles in ARG transmission, and ARB sensitivity to advanced treatment. By comprehensively examining ARB and ARG fate, effective treatment processes can be better targeted.